ok, I see. A problem with LyX. Write into the preamble:
\newtheorem{theorem}{FrenchTheorem} \let\thm\theorem
It works almost perfectly. Without inserting "\let\thm\theorem" in the preamble, the output DVI file displays "Theorem 0.1" whereas otherwise it appears "FrenchTheorem 1.". It seems that anything was changed in the theorem numbering.
change the first line to
\newtheorem{theorem}{FrenchTheorem}[section]
Herbert
